The original post was using salsa for a mainSHEET.
For the main halyard, the 35' dimension is a start, but I'm assuming he'll need a knot or a splice at one end to attache to the sail, then wraps around a cleat and a winch if it stops at the mast like this one
70' won't cut it. 82' is pushing it.
I can measure a triangle. I was suggesting he builds a halyard to real life requirements as opposed to I or P measurements.
My mistake on referencing a jib halyard dimension, you're right the main won't need quite as much, but still way more than 70'.